Innate defense against HIV[unreadable] Mucosal associated lymphoid tissues are major targets of HIV during early infection and disease progression, and can also provide a viral safe haven during highly active antiretroviral therapy. Among these tissues, the tonsils remain enigmatic regarding their status as primary and/or secondary sites of retroviral infection, particularly since oral HIV transmission appears rare. To dissect the mechanisms underlying accessibility and susceptibility to HIV in this compartment, we dissected the epithelium with laser capture microdissection (LCM) and performed microarray gene expression analyses. Our studies demonstrated that the tonsil epithelium is a unique site and exhibits heightened potential for HIV transmission compared to other oral epithelia, likely due in part, to increased HIV co-receptor CXCR4 and reduced antiviral SLPI. To identify selective factors that favor the tonsil lymphoid cells as a viral reservoir, we compared isolated tonsil cell susceptibility to that of blood lymphocytes. In these studies, we identified several unique aspects of the tonsil micromilieu that may support its permissive nature, including elevated levels of Th2 cytokines and limited Th1 cytokines compared with PBMC. Despite elevated levels of antiviral IFN, the tonsil was not able to mount an effective antiviral response after exposure to HIV in vitro, nor apparently in vivo, which may reflect constitutive expression of negative regulators of IFN signaling, such as SOCS. SOCS appear to contribute to the blockade of IFN signaling cascades in the tonsil, evident by the reduced phosphorylation of Stat1, which may account for the local disengagement of IFN signaling and reduced antiviral activity. In a cyclic pattern, SOCS3 may also promote Th2 polarization. Such a profile of immune regulation is consistent with the necessity to control immune activation, yet maintain a state of readiness in an environment constantly bombarded with antigens. In ongoing studies, the tonsil multinucleated and mononuclear cells that produce striking amounts of HIV are being isolated and studied, as is the potential involvement of Treg as regulators and targets for the virus. Further understanding of these populations and the immunoregulatory pathways that influence their susceptibility to HIV pathogenesis are important for protecting vulnerable mucosal compartments from serving as reservoirs for the virus.[unreadable] [unreadable] In earlier studies, we demonstrated that a synthetic triterpenoid and peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), known to influence p21 kinase inhibitor expression (linked to viral life cycle), suppressed viral replication in macrophages and PBMC. Recently, a new methyl ester derivative of CDDO (CDDO-Me), which is uniquely orally bioavailable, has been synthesized and in preliminary phase I trials in cancer patients, it has been shown to not have significant toxicities, consistent with the possibility of testing this agent in HIV patients. Of considerable interest is the evidence that this methyl ester derivative targets the tissues, rather than the blood, and therefore we have focused on defining its ability to inhibit HIV in tonsil tissue derived CD4+ HIV target cells. As anti-retroviral therapy is often characterized by high toxicity and frequently results in the emergence of drug resistant virus strains, the identification of new anti-viral agents targeting host cell molecules that can be used independently or in conjunction with current anti-viral drugs will provide additional resources in the treatment of HIV infection.[unreadable] [unreadable] In additional clinical studies, we have been collaborating with investigators at NIAID in the treatment of AIDS patients with IFN in an attempt to define the antiviral mechanisms by which IFN suppresses HIV burden. In concordance with our in vitro data that IFN potently upregulates members of the cytidine deaminase family of innate intracellular proteins, we show that this also occurs in the PBMC of treated patients. Apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G), a cytidine deaminase with lethal activity against HIV is packaged into progeny virions and leads to HIV cDNA degradation. As a counterattack, HIV virion infectivity factor (Vif) targets APOBEC3G for proteasomal proteolysis, thus excluding its incorporation into budding virions. We found that IFN treatment increased APOBEC3G and other family members, while reducing patient viral load. The maximal magnitude of viral decline occurred during the first week after treatment, especially in patients with lower viral load, comparable to that of early protease inhibitors. Thus, further consideration of a role for IFN as an inductive therapy in the context of low viral loads may be warranted and additional clinical studies are in progress. Moreover, through the use of microarrays, we have identified additional molecular targets of IFN that may contribute to its antiviral effects and may be considered as additional intervention approaches.